Zdeňka Kyjovská

Identification of resistance genes against powdery mildew in four accessions of Hordeum vulgare ssp. spontaneum

SummaryFour newly detected accessions of wild barley (Hordeumvulgare ssp. spontaneum) resistant to powdery mildew caused by Blumeriagraminis f. sp. hordei were studied with the aim of finding the number of genes/loci conferring the resistance of individual accessions, the type of inheritance of the genes and their relationships to the Mla locus. F2 populations after crosses between the winter variety ‘Tiffany’ and four wild barley accessions and use of microsatellite DNA markers were focused on the identification of individual resistance genes/loci by means of their chromosomal locations. In PI466495, one locus conferring powdery mildew resistance was identified in highly significant linkage with the marker Bmac0213. This location is consistent with the known locus Mla on chromosome 1HS. In the other three accessions the resistance was determined by two independent loci. In PI466197, PI466297 and PI466461, one locus was identified on chromosome 1HS and three new loci were revealed on chromosomes 2HS (highly significant linkage with Bmac0134), 7HS (highly significant linkage with Bmag0021) and 7HL (significant linkage with EBmac0755). Our prospective aim is identification of further linked DNA markers and the exact location of the resistance genes on the barley chromosomes.

New Embryo Lethals in Arabidopsis thaliana: Basic Genetic and Morphological Study

Six different mutations with defects in immature seed development have been identified during screening of a T-DNA collection of Arabidopsis thaliana. The mutations were confirmed to be monogenic and recessive-lethal by genetic analysis. Mutant embryos were blocked in certain steps in the process necessary for embryo viability and development, and therefore they belong to the embryo-lethal class of mutants. The genetic and morphological studies of T-DNA mutations affecting embryo development are presented. The youngest embryos with a defect were observed at the globular stage in the VIII-64 mutation. Externally located cells, precursor of the protoderm, were characterised by abnormal cell division. VIII-41 mutation with a defect at the late globular stage was arrested at the globular-heart stage transition. VIII-111 mutation showed defect at heart stage of embryogenesis with atypical development of cotyledon primordia. The defect was associated with abnormal pattern of cell division constituting the precursor of the shoot apical meristem. In VIII-82 mutation defect in torpedo stage with asymmetric cotyledons was observed. Cotyledon stage of embryos and chlorophyll defect were observed in VIII-75 mutant. Abnormal suspensor consisting of two columns of cells was observed in 280-4-4 mutation. Newly identified embryo-lethals can serve as starting material for more detailed genetic and molecular studies.